Study genetically homogeneous cell lines transformed by wild type and mutant polyoma viruses. Maximal growth levels shall be studied in vitro of BHK and BHK transformed by WT and ts-3 polyoma viruses; Electron microscopic studies shall be performed and density-dependent, serum, or pH efects shall be analyzed if encountered, Analysis of cell adhesion properties and studies of growth effectors shall also be undertaken. Specific cell parameters to be investigated shall include regulation of growth levels in vitro, control of cell surface morphology, cellular shape characteristics, formation of microtubules as assessed by S.E.M. and T.E.M. and regulation of strength and specificity of cell adhesion.